Bravo drive propeller shaft

ABSTRACT

A propeller drive system for V-hull and catamaran racing vessels including an offshore racing cleaver propeller run on a water&#39;s surface by means of a long, thick propeller shaft coupled with a Bravo Drive.

CROSS-REFERENCE TO RELATED APPLICATIONS

None

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Research and development of this invention and Application have not been federally sponsored, and no rights are given under any Federal program.

REFERENCE TO A MICROFICHE APPENDIX

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to sterndriven marine vessels, in general, and to an improved propeller drive system for V-hull and catamaran racing and/or pleasure vessels, in particular.

2. Description of the Related Art

As will be appreciated by those skilled in the art, the Bravo Drive form of propulsion developed for high performance marine vessels would be more attractive for use in the Offshore Racing Circuit were it not for the fact that while it may increase a vessel's speed, it also tends to fail quickly. My analyses and testings have shown that this premature failure results from a high frequency harmonic caused by propeller slippage—which also makes it more difficult for the operator to stabilize a vessel's path of direction. At high speeds, such failure could very well lead to the possibility of crashes, injuries and deaths; at the very least, it could result in significant vessel and component damage.

As will also be appreciated, these problems can become all the worse as the propeller shaft is sought to be raised from below the water line in an attempt to enhance higher performance and obtain higher speed from the vessel. This follows because it is accompanied by even higher slippage and greater vibration.

As will become clear from the following description, the improved propeller drive system of this invention allows a racing vessel to run approximately 10 miles per hour faster, without failure or damage to the propeller. A reduction of slippage from the 14-16 percent common to the Bravo Drive down to approximately 4 percent also will be understood to result, significantly decreasing propeller vibration.

SUMMARY OF THE INVENTION

To understand the advance of the present invention, it must first be appreciated that the original development of the Bravo Drive by Mercury Marine utilized a propeller intended to run submerged below the water line. In trying to increase the vessel's speed toward 80, 90 and 100 miles per hour, the installation was changed to run the propeller on the surface, utilizing a different Mirage or Maximus propeller. However, with one blade of these propellers being out of the water at any instant of time, these propellers became unevenly loaded, with the impact in its striking the water then eventually damaging the shaft to breakage—with the resulting loss of the propeller. My analysis showed that with these propellers being of a 30 inch pitch, running them in the water produced a slippage of between 14 and 16 percent; and it was this harmonic vibration which threw the propeller out of balance and eventually over time destroyed the entire drive. Substituting, instead, a propeller intended to be run on the surface seemed to be an possible solution as its increased blade area would bring the slippage down, leading to less harmonic vibration. But this suffered disadvantages of its own: a) first of all, in increasing the cost from the Bravo Drive of approximately $8,000.00 to one of $35,000.00 if a Mercury Marine #6 Drive were used instead; and b) secondly, such a substitute drive would require a significant increase in horsepower to reach the same vessel speeds. The result would then be that a 36 foot boat with a #6 Drive would cost approximately $400,000.00, as compared to $250,000.00 for the Bravo Drive vessel. However, even so, #6 Drives are not user friendly to many vessels, at least due in part to their mass and weight.

As will be seen from the description that follows, the present invention sets out a new and improved propeller shaft and bearing carrier for a Bravo Drive. This will be appreciated to allow the vessel to use an offshore racing cleaver propeller of a type meant to run on the surface. Being of a design whose blades leave and enter the water more smoothly, the resultant slippage and vibration are reduced. Being more massive, a longer invention, to fit the shaft is used as well.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features of the invention will be more clearly understood from a consideration of the following description, taken in connection with the accompanying drawings, in which:

FIG. 1 pictorially illustrates a stern driven, Bravo Drive motor with its propeller removed, typifying the prior art;

FIG. 2 is a top view of an offshore racing cleaver propeller utilized in accordance with the present invention;

FIGS. 3 a and 3 b respectively illustrate the propeller shaft of the Bravo Drive of FIG. 1, and the longer, thicker, propeller shaft of the invention;

FIGS. 4 a and 4 b illustrate the bearing carrier of the type employed in the prior art arrangement of FIG. 1, and as used according to the invention, respectively;

FIG. 5 is a schematic drawing helpful in an understanding of the increased size of the propeller shaft of the invention; and

FIGS. 6 a, 6 b and 6 c are schematic diagrams of the front, side and rear views of the bearing carrier of the invention helpful in an understanding of its construction.

DETAILED DESCRIPTION OF THE INVENTION

Referring to the Drawings, the propeller shaft 10 of FIG. 3 b and of FIG. 5 will be understood to be longer and thicker than the prior art propeller shaft 11 of FIG. 3 a so as to support the offshore racing cleaver propeller 12 of FIG. 2. Although such propeller is shown as having four blades 14, the improvement of the invention will be appreciated to extend still further where five and six blade cleaver propellers are employed. Such blades enter the water smoothly during its rotation in mellowing the motor down more slowly, and exhibit a slippage of some 4 percent. In one construction of the invention, a 16.5 diameter, 31 inch pitch four blade propeller was employed, while in a second construction, a 16.5 diameter, 35 inch pitch blade was utilized. With them installed, and with the propeller shaft 10 of FIGS. 3 b and 5 being utilized with the bearing carrier of FIGS. 6 a-6 c, vessel speeds in excess of 160 mph have been reached without suffering any failure or damage. The use of such cleaver propellers allows the propeller shaft 10 to run above the water line—and, in accordance with the teachings of the invention, have been set to extend as far as 2½ inches above the bottom of the boat. This is to be contrasted with the typical Bravo Drive where the propeller shaft 11 runs below the water line—although in some high performance applications, they have been installed to run even with the water line. As will be appreciated, such installations lead to the high slippage, the harmonics, and the unsafe conditions which accompany the premature Bravo Drive failures that result as the boats are driven at increased speeds. With the cleaver propeller of the present invention, higher speeds are attained, with decreased slippage, and significantly reduced drive failure.

While Applicant does not wish to be restricted to any particular set of dimensions, the following dimensions for the propeller shaft 10 of FIG. 5 have proven quite useful:

-   Dimension 101 . . . 1.125 inches -   Dimension 102 . . . 2.000 inches -   Dimension 103 . . . 2.300 inches -   Dimension 104 . . . 2.500 inches -   Dimension 105 . . . 2.600 inches -   Dimension 106 . . . 3.600 inches -   Dimension 107 . . . 4.500 inches -   Dimension 108 . . . 7.575 inches -   Dimension 109 . . . 8.675 inches -   Dimension 110 . . . 16.100 inches -   Dimension 111 . . . 17.100 inches -   Dimension 112 . . . 17.100 inches -   Dimension 113 . . . 18.400 inches -   Dimension 114 . . . 1.250 inches -   Dimension 115 . . . 1.558 inches -   Dimension 116 . . . 1.440 inches -   Dimension 117 . . . 2.350 inches -   Dimension 118 . . . 1.970 inches -   Dimension 119 . . . 1.870 inches -   Dimension 120 . . . 1.000 inches -   Dimension 121 . . . 1.666 inches -   Dimension 122 . . . 45 degrees -   Dimension 123 . . . 45 degrees -   Dimension 124 . . . 45 degrees     The propeller shaft 10 may be manufactured of chrome finished, heat     treated stainless steel. Preferably, it is of a length of     substantially 18.400 inches, and of a girth at its widest part of     substantially 2.350 inches. At its splined first end 15, the shaft     10 is of a diameter of substantially 1.125 inches, and at its     threaded end 16 where the cleaver propeller 12 rides, the propeller     shaft 10 is of a diameter of substantially 1.000 inches. With these     dimensions, the shaft 10 is of a length and girth to ride to a     height of 2½ inches above the water through which the boat is     propelled.

FIGS. 6 a-6 c illustrate the bearing carrier 18 of the invention for fitting the longer, thicker propeller shaft 12 to the motor drive 20 of FIG. 1. Manufactured of aircraft 2024 aluminum billet, hard anodized steel, the bearing carrier (Shown as 22 in FIG. 4 b), replaces that more commonly employed, shown as 24 in FIG. 4 a. With the present invention, the following dimensions have proved useful in accepting the propeller shaft 10 of FIG. 5 with the Bravo Drive unit:

-   Dimension 201 . . . 4.305 inches -   Dimension 202 . . . 3.700 inches -   Dimension 203 . . . 2.900 inches -   Dimension 204 . . . 2.100 inches -   Dimension 205 . . . 2.501 inches -   Dimension 206 . . . 3.540 inches -   Dimension 207 . . . 3.550 inches -   Dimension 208 . . . 3.865 inches -   Dimension 209 . . . 4.283 inches -   Dimension 210 . . . 4.900 inches -   Dimension 211 . . . 4.000 inches -   Dimension 212 . . . 3.900 inches -   Dimension 213 . . . 2.900 inches -   Dimension 214 . . . 1.100 inches -   Dimension 215 . . . 0.250 inches -   Dimension 216 . . . 0.125 inches -   Dimension 217 . . . 2.500 inches -   Dimension 218 . . . 3.625 inches -   Dimension 219 . . . 3.700 inches -   Dimension 220 . . . 4.700 inches -   Dimension 221 . . . 4.150 inch diameter     Dimension 2o5 in FIG. 6 b is that for the seal seat, while Dimension     206 is for the bearing seat. Dimension 224 in this construction is a     ¼ inch radius, while angle 225 is of 28 degrees.

As will be appreciated by those skilled in the art, the teachings of the present invention allow a designer to run more horsepower than the Bravo Drive was designed for, although not as much as with the Mercury Racing Six Drive. The invention also will be seen to allow one to run the vessel at higher speeds than with the prior constructed Bravo Drive, yet without its slippage and possible drive failures. Although less able to reach the speeds of the Mercury Racing Six Drive, the teachings of the invention allow a significant savings as associated with the latter's increased cost—and thus effectively fills a gap between the Bravo Drive and the Racing Six Drive.

While there have been described what are considered to be preferred embodiments of the present invention, it will be readily understood by those skilled in the art that modifications can be made without departing from the scope of the teachings herein. For at least such reason, therefore, resort should be had to the claims appended hereto for a true understanding of the invention. 

1. A stern mounted propulsion system for a marine vessel comprising: a Bravo unit drive motor; a bearing carrier at an output end of said motor; a propeller shaft coupled to said motor via said bearing carrier, having a splined first end and a threaded second end; and an offshore racing cleaver propeller on said threaded second end.
 2. The propulsion system of claim 1 wherein said propeller shaft is coupled to said motor in running said cleaver propeller on the surface of the water through which the vessel is propelled.
 3. The propulsion system of claim 2 wherein said cleaver propeller is composed of one of four, five and six blades.
 4. The propulsion system of claim 2 wherein said cleaver propeller is of a four-blade construction, of 16.5 inch diameter.
 5. The propulsion system of claim 4 wherein said cleaver propeller is one of a 31 inch and 35 inch pitch.
 6. The propulsion system of claim 2 wherein said propeller shaft is of a length and girth to ride above the surface of the water through which the marine vessel is propelled.
 7. The propulsion system of claim 2 wherein said propeller shaft is of a length and girth to ride to a height of 2½ inches above the surface of the water through which the marine vessel is propelled.
 8. The propulsion system of claim 6 wherein said propeller shaft is of a length of substantially 18.400 inches and of a girth at its widest part of substantially 2.350 inches.
 9. The propulsion system of claim 8 wherein said threaded second end of said propeller shaft is of a diameter of substantially 1.000 inches.
 10. The propulsion system of claim 9 wherein said splined first end of said propeller shaft is of a diameter of substantially 1.125 inches.
 11. The propulsion system of claim 10 wherein said propeller shaft is composed of chrome finished, heat treated stainless steel. 